An optical module known in the related art optically couples a planar optical device configured to emit or receive light in a direction substantially perpendicular to a substrate and an optical waveguide configured to guide light in a direction parallel to the substrate. A technology included in such an optical module disposes optical devices two-dimensionally by shifting the positions of the optical devices so as to reduce the pitch of the optical devices to be narrower than that of optical waveguides. See, e.g., U.S. Pat. No. 7,474,815.
Also, a technology known in the art mounts optical elements on the opposite sides of an optical waveguide to sandwich the optical waveguide therebetween in which the light coupled to the optical element disposed on the first side of the optical waveguide and the light coupled to the optical element disposed on the second side of the optical waveguide are propagated in opposite directions within the optical waveguide. See, e.g., Japanese Patent Laid-open Publication No. 2006-120956.
In addition, a technology known in the art optically couples an optical fiber and an optical element by forming a recess inclined at 45 degrees on the core of the optical fiber, installing a mirror in the recess, and disposing the optical element directly above the mirror. See, e.g., Japanese Patent Laid-open Publication 2005-331702.
Furthermore, a technology known in the art optically couples an optical element and an optical fiber by disposing optical elements on the sides of the optical fiber to sandwich the optical fiber therebetween in which light is totally reflected by a total reflection plane. See, e.g., Japanese Patent Laid-open Publication No. 2012-032509.